This invention relates to a tape reel for a tape cassette, and more particularly to a tape reel adapted to be rotatably incorporated in a tape cassette to take up a tape thereon and deliver it therefrom.
A conventional tape reel used for such a purpose includes a reel flange, which is provided on a bottom surface thereof or a surface thereof opposite to a tape receiving surface thereof with reinforcing ribs in a manner to radially or concentrically extend thereon in order to prevent deformation of the reel flange due to a weight of a tape wound on the tape reel, as disclosed in, for example, Japanese Utility Model Application Laid-Open Publication No. 80747/1979.
However, an increase in width of the reinforcing rib to a level larger than a thickness of the flange causes sink marks to occur on a surface of the flange on which the ribs are not provided or the above-described tape receiving surface of the flange. Thus, in the conventional tape reel, it is required that the reinforcing ribs are formed with a width equal to or smaller than a thickness of the reel flange. Also, a weight-saving of the tape reel for the purpose of reducing a manufacturing cost thereof requires to reduce a thickness of the reel flange and concurrently reduce a width of the reinforcing ribs to avoid any sink mark.
Unfortunately, the conventional tape reel in which the reinforcing ribs are radially or concentrically arranged while reducing a thickness of the flange causes an increase in warpage of the flange and/or deflection thereof when a cycle time of molding the tape reel is shortened or reduced; whereas a variation in shape of an inner side of a reel stabilizing surface of the tape reel and/or shape of the ribs or an increase in the number of ribs causes an increase in weight of the tape reel. Thus, the conventional tape reel fails to uniformly reinforce the whole flange while keeping a weight of the flange from being increased. In particular, when the reinforcing ribs formed on the flange for the purpose of preventing any sink mark of the flange are reduced in width, the flange fails to exhibit sufficient strength or stiffness; so that a weight of a tape wound on the tape reel causes deformation of the reel flange. Such deformation is amplified during storage of the tape reel at a high temperature.